We do not fully understand the molecular mechanisms that help protect humans against UV. Much of our current knowledge in this area has been derived from studies in bacteria and yeast. The general aim of this project is to use the plant Arabidopsis as a model system to increase our understanding of the molecular basis of the adaptive responses of biological systems towards UV-stress. The choice of this organism is based on its being amenable to molecular as well as classical genetics studies. The overall plan is to find and isolate genes involved in the protective responses against UV-radiation; to analyze these genes and study their function in order to determine the role they play in UV-resistance; and ultimately to investigate the mechanisms that modulate their expression in response to UV-radiation. The approach being taken is two fold: 1. To isolate and analyze mutants displaying altered resistance to UV-radiation; and 2. To directly obtain clones of genes that become activated in response to UV-radiation. A mutant has been found which shows a drastic increase in sensitivity to UV-radiation because of a block in the accumulation of various UV-absorbing flavonoids. Specifically, the goals are to engage MBRS students in both approaches by assigning them, according to their interests, skills and career goals, to one of the following projects: 1. To determine the identity of the UV-absorbing flavonoids which are missing in the UV-sensitive mutant. 2. To determine which enzymatic activity in the flavonoid biosynthetic pathway has been blocked in the mutant. 3. To genetically map the affected gene to a specific chromosomal location. 4. To analyze the different parameters that govern the UV-induced increase in flavonoid levels, especially with regard to the quality of the UV-signal. 5. To begin the second approach to define other UV-tolerance genes. Because of my Hispanic background, experience, and scientific interests, I feel I can efficiently guide and motivate minority students to become seriously involved in research; successfully complete their project and seriously consider pursuing a career in biomedical research.